1. Field of the Invention
The present invention relates to a vibration-isolating composite material.
2. Description of the Prior Art
Recently, vibrations have been developed into a great social problem awaiting a solution. Further, in precise processing carried out by use of optical instruments, laser devices or the like, very small vibrations have a great influence on quality of products. In order to minimize disadvantages due to vibrations, there have been proposed various measures against vibrations. For example, it has been proposed to improve the stiffness of devices serving as a source of vibrations. Also, it has been proposed to provide a means for preventing the precise devises from sympathetic vibrations or a means for isolating vibrations.
The most popular vibration isolating means is to use a vibration-isolating material which reduces vibrations applied. As such a vibration-isolating material, there have been used rubbers, damping metals (generally, alloys) and composite ferrite materials. According to the theory of vibration, a vibration-isolating material to be used is required to meet the requirements that it has a large mass, large energy loss ratio of vibration transmission and logarithmic decrement, and large elastic modulus.
The vibration-isolating materials of the prior art satisfy some of the aforesaid requirements, but none of them satisfy all the requirements. For example, the rubbers are large in logarithmic decrement but small in elastic modulus. Contrary to this, the damping metals are very large in elastic modulus but small in logarithmic decrement. Further, the ferrite composite materials are large in both the logarithmic decrement and elastic modulus, but they cannot be accepted as a material for use in very high precise apparatus. This is because the ferrite composite material is magnetized with orientation due to ferromagnetic material contained therein so that vibration-isolating articles made of such ferrite composite material would cause magnetic flux which has a considerable influence on the properties of the precise apparatus.
U.S. Pat. No. 4,595,515 discloses a composite material for vibration-insulating articles comprising a high polymer with a powdered organic or inorganic piezoelectric material dispersed therein, and having electrical leakage paths provided therein. In such a composite material, vibration energy applied thereto is first converted by the piezoelectric effect of the piezoelectric material into electric energy or charges, and the produced electric charges are converted into thermal energy while flowing through the electrical leakage paths and consumed as heat.
However, the above composite material can not applied to vibration-insulating articles used for the very high precise instruments sensitive to electric charges since the composite material generates electric charges by vibration.